(a) Field of the Invention
The invention relates to a continuous process for the denaturation of proteins using dynamic high-pressure homogenization (HPH).
(b) Description of Prior Art
Whey proteins have been extensively studied for their structure and functional properties. Most of researchers have shown that whey proteins undergo denaturation when heat-treated at temperatures exceeding 60xc2x0 C. (De Wit et al., 1988, IDF Symposium Quebec, Canada, 129-148). Recently, denaturation, aggregation and gelation processes of whey proteins have been described in three steps. The first step involves the unfolding of molecules followed by a second step which is related to the aggregation process of partially unfolded whey proteins. The last step involves the polymerization of the protein network which leads to gelation.
The use of high hydrostatic pressures on whey protein solutions have been reported to initiate protein-unfolding and result in gelation of protein solutions without heat-treatments (Hayakawa et al., 1992, J. Food Sci., 57:288-292; Johnston et al., 1992, Milchwissenchaft, 47:760-763). In these cases, the pressure caused a volume reduction in the solution which led to a reorganization of hydrogen bonds and hydrophobic interactions (Hoover et al., 1989, Food Technol., 43:99-107).
High-shear forces have also been shown to affect protein denaturation, as demonstrated by studies on denaturation of protein solutions by extrusion (shear forces) (Rha and Pradipasena, 1977, J. Texture Stud., 8:339; Ker and Toledo, 1992, J. Food Sci., 57:82-89; Taylor and Fryer, 1994, Food Hydrocolloids, 8:45-61). These results show that both high pressure (static) and shear forces can modify proteins by partial denaturation. However, these studies did not demonstrate that the use of both high pressures and shear forces together have a specific effect on the proteins. Also, static high pressure is limited because it is done in a batch system and not in a continuous process.
To date, there has not been shown a continuous process for the denaturation of proteins using dynamic high-pressure homogenization (HPH).
It would be highly desirable to be provided with partial or total denaturation of proteins using a continuous process consisting in a combination of shear forces cavitation and turbulences at high pressures with a very short heat treatment (milliseconds) in the reaction chambers of a high-pressure homogenization (HPH) equipment.
One aim of the present invention is to provide a continuous process for the denaturation of proteins using dynamic high-pressure homogenization (HPH).
Another aim of the present invention is to provide partial or total denaturation of proteins using a continuous process consisting in a combination of shear forces cavitation and turbulences at high pressures with a very short heat treatment (milliseconds) in the reaction chambers of a high-pressure homogenization (HPH) equipment.
The process of the present invention is used on food proteins to produce partial or total denaturation of proteins. The proteins are modified by the effect of dynamic high-pressure and possess different functional properties, such as solubility, emulsification, foaming or gelation, which in turn affect their use in food products (mayonnaise, salad dressing, meat emulsion, foam and mousse, among others).
In accordance with the present invention there is provided a continuous process for denaturation of proteins, which comprises the steps of:
a) subjecting a protein solution to a high pressure homogenizer at a pressure of about 500 to about 5000 bar, at a recirculation ranging from 0 to about 50 and at a temperature ranging from about 20xc2x0 C. to about 80xc2x0 C. for a period of time from about 1 milliseconds to about 10 minutes, wherein the protein solution consisting of a protein fraction dispersed in water, buffer or salt solution at a concentration ranging from about 2% to about 35% w/w and at a pH adjusted between about 2.0 to about 12.0;
b) concentrating the protein solution by i) evaporation, ii) ultrafiltration and sprayed dried or iii) ultrafiltration and freeze dried.
The denaturation may be partial or total.
The protein fraction may be selected from the group consisting of egg, milk, and vegetable.
The preferred milk protein is whey protein.
The protein may be a protein concentrate at a concentration about 35% to about 99%.
The whey protein is a whey concentrate or a whey isolate.
The whey protein is at a concentration about 35% to about 99%.
The preferred pH ranges between 6.0 to about 7.0 and the preferred protein fraction is at a concentration of about 5% to about 14%.
The preferred pressure is more than 1500 bar, the temperature is 22xc2x0 C. or 55xc2x0 C. and the preferred recirculation is ranging from 1 to 5.
In accordance with the present invention there is provided a food protein composition, which comprises partially or totally denatured protein with enhanced viscosity and gel firmness properties, with higher solubility, wherein the protein is obtained by the process of the present invention.
For the purpose of the present invention the following terms are defined below.
The term xe2x80x9chigh homogenization pressurexe2x80x9d is intended to mean a pressure between about 500 to about 5000 bar, with a preferred pressure of about 3 kbar.
The preferred protein used in accordance with the process of the present invention is whey protein.